This specification is related to devices and systems with electronic processors, and more specifically, to mobile computer systems.
A mobile computer has traditionally been a less powerful substitute for a regular desktop computer. However, advances in mobile computer technology have made performance of many mobile computers comparable to that of their desktop counterparts. One convenient feature of mobile computers is that they are mobile and can be operated wherever the user may desire, on battery power without AC power. However, a battery can store only a limited amount of energy. The operating time of a mobile computer in the battery operation mode is approximately inversely proportional to the power consumed by the mobile computer. It is therefore desirable to reduce the power consumption.
Many mobile computers use a single microprocessor and have system configurations similar to those of single-processor desktop computers. In order to reduce power consumption, mobile computers often implement a number of power-saving mechanisms. For example, a mobile computer may be put into a standby mode or a suspended mode in which certain functions of the microprocessor and operations of other components (e.g., the spinning motion of the hard drive or the optical storage disk) may be stopped or the power to certain devices and components may be turned off. Hence, the system operates at a low power level. The operating voltage of the power supply and the CPU clock frequency of the microprocessor may also be changed to a set of predetermined low values whenever permissible to save the battery power and to extend the battery operation time.
The present disclosure includes special system architectures that implement at least two processors. One embodiment of such computer systems includes a first processor of a first clock frequency and a first level of power consumption, and a second processor of a second clock frequency and a second level of power consumption. The second clock frequency and second level of power consumption are respectively less than the first clock frequency and first level of power consumption.
An interface circuit is coupled to control the first and second processors and is configured to select one of the first and second processors to operate at a time. The electric power to the first processor is turned off when the second processor is selected to operate.
Such a system can be used to extend the operating time when powered by a battery.